System and method for determining physiological parameters based on electrical impedance measurements

1. A method for separating measurement signals, the method comprising: coupling a plurality of transducers on a surface of an object, the plurality of transducers comprising at least two excitation transducers and at least two measuring transducers; generating excitations on at least a subset of the plurality of transducers, the excitations driven in different configurations from at least one of the two excitation transducers; obtaining measurement response signals at a response detector, as acquired from the subset of the plurality of transducers; spatially pre-conditioning the obtained measurement signals to convert the measurement response signals into spatial vectors; performing multiple-input-multiple-output (MIMO) analog to information conversion (AIC) of the spatially pre-conditioned measurement signals to correlate the spatially pre-conditioned measurement signals in order to separate the measurement signals of a sub-space of desired physiological activities, as distinguished from a sub-space of undesired signals; wherein inputs of the MIMO AIC are the spatial vectors, and the MIMO AIC identifies and then tracks the sub-space of the desired physiological activities; and classifying the measurement signals of the sub-space of desired physiological activities as respiratory information and classifying the sub-space of undesired signals as ambulatory motion information.

2. The method of claim 1 , wherein the measurement response signals are electrical measurement response signals, and the MIMO AIC of the spatially preconditioned electrical measurement signals comprises a multi-channel sigma-delta (EA) MIMO AIC.

3. The method of claim 2 , wherein the output of the MIMO AIC comprises digitized de-correlation coefficients of the electrical measurement signals and an uncorrected output data stream.

4. The method of claim 2 , wherein spatially pre-conditioning the obtained electrical measurement signals comprises using a common mode averaging of all of the electrical measurement signals.

5. The method of claim 2 , wherein the electrical measurement signals are obtained from electrodes in an electrocardiography (ECG) electrode placement configuration.

6. The method of claim 1 , wherein classifying the sub-space of undesired signals as ambulatory motion information includes identifying at least one of a type of motion or a position.

7. The method of claim 6 , wherein the ambulatory information includes an identification of at least one of breathing, bending, twisting, or reaching motion.

8. The method of claim 6 , wherein the ambulatory motion information includes an identification of at least one of a supine position, seated position, or standing position.

9. The method of claim 1 , further comprising using an output of the MIMO AIC and multi-lead transducer signals to determine an ambulatory motion index.

10. The method of claim 1 , wherein the excitations comprises one of an electrical, magnetic, or radio-frequency excitation.

11. The method of claim 10 , wherein obtaining the electrical measurement signals comprises measuring at least one of an electrical voltage, current, magnetic response or radio-frequency response on all or a subset of the plurality of transducers.

12. A method for monitoring breathing, the method comprising: positioning a plurality of transducers on a surface of a person, the plurality of transducers comprising at least two excitation transducers and at least two measuring transducers; generating excitations on at least a subset of the plurality of transducers, the excitations driven in different configurations from at least one of the two excitation transducers; obtaining measurement response signals at a response detector, as acquired from all or the subset of the plurality of transducers; spatially pre-conditioning the obtained measurement signals to convert the measurement response signals into spatial vectors; and then performing multiple-input-multiple-output (MIMO) analog to information conversion (AIC) of the measurement signals to correlate the measurement signals of a sub-space of desired physiological activities as breathing signals and measurement signals of a sub-space of undesired physiological activities as ambulatory motion signals; wherein inputs of the MIMO AIC are the spatial vectors, and the MIMO AIC identifies and then tracks the breathing signals and the ambulatory motion signals; and classifying the measurement signals of the sub-space of desired physiological activities as respiratory information and classifying the sub-space of undesired signals as ambulatory motion information.

13. The method of claim 12 , further comprising pre-conditioning the measurement signals prior to performing the MIMO AIC.

14. The method of claim 12 , wherein the measurement signals are obtained simultaneously or sequentially.

15. The method of claim 12 , wherein the MIMO AIC of the spatially pre-conditioned measurement signals comprises a multi-channel sigma-delta (ΣΔ) MIMO AIC integrated into an impedance based respiratory rate monitoring system.

16. The method of 15 , wherein the output of the MIMO AIC comprises digitized de-correlation coefficients of the measurement signals and an uncorrected output data stream.

17. The method of claim 12 , further comprising using an output of the MIMO AIC and multi-lead transducer signals to determine an ambulatory motion index.

18. The method of claim 17 , further comprising using the ambulatory motion index and the separated measurement signals in a weighting process to classify different types of breathing.

19. An impedance measurement system comprising: a plurality of transducers configured for positioning at a surface of an object, the plurality of transducers comprising at least two excitation transducers and at least two measuring transducers, wherein the plurality of transducers correspond to a plurality of channels; an excitation driver coupled to at least a subset of the plurality of channels and configured to generate excitations on at least a subset of the plurality of transducers in different configurations from at least one of the two excitation transducers: a response detector configured to measure a response on at least a subset of the plurality of transducers to define measurement signals; and a processor having a physiological parameter extraction module that uses multiple-input-multiple-output (MIMO) analog to information conversion (AIC) of the measurement signals to correlate the measurement signals in order to separate the measurement signals of a sub-space of desired physiological activities, as distinguished from a sub-space of undesired signals; wherein the processor is configured to pre-condition the measurements signals prior to the MIMO AIC using a signal pre-conditioner that utilizes spatial differentiation; wherein the MIMO AIC identifies and then tracks the sub-space of the desired physiological activities; and wherein the processor is configured to classify the measurement signals of the sub-space of desired physiological activities as respiratory information and classify the sub-space of undesired signals as ambulatory motion information.

20. The impedance measurement system of claim 19 , wherein the physiological parameter extraction module is further configured to identify at least one of physiological parameters and non-physiological parameters using the separated measurement signals, wherein the separated measurement signals are electrical measurement signals.

21. The impedance measurement system of claim 19 , wherein the plurality of transducers comprise electrodes coupled to skin of a patient in an electrocardiography (ECG) electrode placement configuration.

22. The impedance measurement system of claim 19 , wherein the plurality of transducers comprises one of electrical, magnetic or radio-frequency transducers.

23. The impedance measurement system of claim 19 , wherein the excitations comprise one of current, voltage, magnetic or radio-frequency excitations and the measurement signals comprises at least one of current, voltage, magnetic and radio-frequency signals.